Bob Hoskins' voice was dubbed over by another actor from Wolverhampton out of fear that Americans wouldn't understand his London accent. After Hoskins threatened to sue Jack Gill and British Lion, the dubbing was removed. He was supported by Richard Burton, Sir Alec Guinness, and Warren Beatty.
Harold's plans for the London docks prophetically predicted the creation of Canary Wharf.
This film is Pierce Brosnan's feature film debut, his part was supposed to be completely silent, but he improvised one word of dialogue, "Hi".
The celebrated line: "There's a lot of dignity in that, going out like a raspberry ripple", was improvised by Bob Hoskins. The original line in Barry Keeffe's script was "...going out like a choc ice", but everyone agreed Hoskins' version was funnier.
Francis Monkman's score is so loud during the final scene that it drowns out any noise, because director John Mackenzie was giving constant verbal direction to Bob Hoskins the entire time. Because sound levels on both sides needed to sync, the producers decided to mute the whole thing and put the score over it.